JP-U-4-105906A shows a valve timing controller of an engine by utilizing a rotation torque of a motor. In the valve timing controller of such a motor utilizing type, a control signal is conventionally generated by a control circuit on the basis of an engine speed signal showing the real rotation speed of the engine, and the motor is electrically turned on and is driven by a driving circuit in accordance with this generated control signal. Here, a detecting signal of a rotation speed sensor for detecting the real rotation speed of the engine is used as the engine speed signal.
However, in the above controller, a detecting lower limit value inevitably exists in the rotation speed sensor of the engine. Therefore, when the real rotation speed of the engine is smaller than the detecting lower limit value, the detecting signal, i.e., the engine speed signal is not outputted from the rotation speed sensor. Therefore, when the real rotation speed of the engine becomes a low rotation speed smaller than the detecting lower limit value, the generation of the control signal using the control circuit and the electrical conducting operation of the motor using the driving circuit cannot be realized.